1. Field of the Invention
The present invention relates to the image correcting apparatus. More particularly, it relates to the apparatus for correcting a white level and a black level of input data fetched through a scanner device based on an optical reference signal.
2. Description of the Prior Art
A scanner device is known that fetches character data and image data, and can display that data onto a monitor such as CRT display, LCD or the like. Such a scanner device is required to correct the white level, the black level and .gamma. characteristics. In the prior art as described in Provisional Publication No. 070,275/1994, it is known that a memory is provided to storage a plurality of correcting data for the .gamma. characteristics and the optimum .gamma. characteristics are selected adaptively to a luminance level of an input signal.
Another type of scanner device (not publicly known technique) that uses a CCD line sensor, detects an optical black reference level by the CCD line sensor and then corrects the black level by using the optical black reference level in the manner of digital process is proposed. However, an apparatus or a method which can correct the black level, the white level and the .gamma. characteristics of digital input data by a simple construction is still not proposed.
Moreover, a light amount correction, a color temperature correction, and a black level correction of a light source regarding input data are executed in different blocks. Since the respective corrections are executed in the different blocks as mentioned above, each block needs an exclusive-use hardware. For this purpose, for example, it is considered that the above-mentioned correcting processes are executed by one CPU (Central Processing Unit). In this case, however, a calculation amount of the contents of processes of the CPU becomes enormous.